Mechanism for protecting boiler feed pump



Oct. 18, 1955 E. T. DAHL. 2,720,838

MECHANISM FOR PROTECTING BOILER FEED PUMP Filed Sept. 22, 1951 5Sheets-Sheet l FIG! IN VEN TOR.

gdwurd T. Dohl fluwyflww ATTORN EYS llllli Oct. 18, 1955 E. T. DAHL2,720,838

MECHANISM FOR PROTECTING BOILER FEED PUMP Filed Sept. 22, 1951 3Sheets-Sheet 3 I! I I v 2a /5 5 4 FIG. 4

FIG?) IN V EN TOR.

l idword T. Dahl ELEV/WM ATTQRN EYS eater-tied Oct. 18, 1955 2,720,838IVIECHANISM FOR PROTECTING BOILER FEED PUMP Edward T. Dahl, WarwickNeck, R. I., assignor, by mesne assignments, to Reconstruction FinanceCorporation, Boston, Mass., a corporation of the United StatesApplication September 22, 1951, Serial No. 247,783 3 Claims. (Cl. 10342)This invention relates to boiler feeds and more particularly to anarrangement for preventing injury to a main feed pump should the feedwater to the boiler be throttled down to a point where the energydeveloped by the pump is not used in useful work.

The invention is particularly intended for a marine type of boiler feedsystem as distinguished from the systems sometimes used in large centralcontrol plants. In the use of a large central power plant, the loadswhich are carried by the plant are known from time to time or hour tohour and their variation is anticipated. No quick changes are involved.There is plenty of time for controls to be put into effect for theboiler feed water. Some elaborate electrical systems are utilized as asafety factor in case the loads vary beyond those anticipated andsuddenly drop to a dangerous minimum. This occurs very infrequently,such as once or twice in five years.

On the other hand, in marine use the changes are sudden and cannot beanticipated by the operators of the engine room of a vessel, especiallyin cases where the vessel is coming slowing into a harbor and suddenchanges of operating conditions are required. Especially does this occurin bringing the vessel to a dock. Conditions must always be ready for afull capacity load, while for a large part of the time the demand forboiler feed water is at a very minimum. Heretofore, it has been usual inthe marine type of installation to provide a bleed from the main feedwater supply back to the source of the water for the boiler in amountsof per cent and sometimes as high as 25 per cent, which means areduction in the efiiciency which is very appreciable when a largeamount of horse power is used. Where the boiler pump feeds are frompumps in the neighborhood of 500 horse power, there would be a loss atthe 15 per cent level of bleed of 75 horse power, which is aconsiderable amount of loss resulting in inefficient operation.

This invention has to do with a system where the boiler feed water issupplied and in which there is a recirculation when the feed to theboiler approaches a dangerous minimum, while the recirculating portionof the system is entirely out off with no recirculating permitted duringthe feeding of water to the boiler in amounts above a dangerous minimumfor the pump to operate on.

One of the objects of the invention is to provide a syster which willautomatically cut in and cut out in response to a metering valve throughwhich the water to the boiler passes.

Another object of the invention is to combine a metering valve and acheck valve so that there will be no reverse flow permitted back to thepump in such situations as where several pumps are operating upon oneline and one of the pumps may fail.

Another object of the invention is to provide a system which, shouldfailures occur, will fail safe from the standpoint of liability ofinjury to any of the units of the system.

Another object of the invention is to provide a system in which theamount of flow of boiler feed water to the boiler will be readilyascertained by looking at the metering valve.

Another object of the invention is to control the recirculating valvefrom a flow meter through a pilot valve which is directly responsive tothe flow meter.

Another object of the invention is to provide a system in which theoperation is in response to the variable area controlling the volume offlow as distinguished from variation of pressures.

Another object of the invention is to provide a control valve from theboiler feed water which will open slowly so as to prevent disruption offeed water controls.

Another object of the invention is to provide an arrangement in whichthere may be a plurality of units connected together with motion takenfrom one unit to operate another unit by transmitting motion from withinthe unit to outside the unit through suitable seals.

With these and other objects in view, the invention consists of certainnovel features of construction, as will be more fully described andparticularly pointed out in the appended claims.

In the accompanying drawings:

Figure 1 is a sectional view of a trolled;

Figure 2 is a sectional view of the control mechanism;

Figure 3 is a sectional view of the valve plug on line 3-3 of Figure 2;

Figure 4 is a diagrammatic view of the system in which the controlmechanism operates.

Referring to the schematic diagram, I have illustrated at 10 a boiler tobe fed with water from a suitable source which, for purposes ofillustration, may be a tank 11 which is provided with sort of apre-heating mechanism for preheating the water supply. From this supply11 a conduit 12 extends through a booster pump 13, thence throughconduit 14 to the main feed pump 15. The discharge from this main feedpump is along the conduit 16 and through a spring-loaded flow-responsivemetering check valve designated generally 17, and thence to the boiler10 through conduit 18. This conduit is controlled by valve 19 which isso arranged that it opens as the demand for the boiler water increasesor is closed down as the water supply becomes sufiicient. Conduit 20leads from the conduit 16 which extends between the pump and themetering valve 17, back to the supply 11 with a motoractuated controlvalve 21 interposed in this line which when open permits feed water tobe transferred or recirculated back to the source 11, the amounttransferred or recirculated being proportional to the amount that thevalve 21 is open. In order that this valve 21 may be controlled as toits amount of opening, I have provided a pilot valve 22 associated withthe metering check valve 17 which is responsive in its action to themetering check valve so as to cause the valve 21 to be open or closemore or less, dependent upon the position of the metering valve. Thecontrol is exercised through some external power supply such, forinstance, as water taken under pressure from the booster pump throughthe conduit 23 which leads to the pilot valve 22 and from the pilotvalve is transfered through conduit 24 to the motor of valve 21.

The recirculating control valve designated generally 21 is shown ingreater detail in Figure 1 and is a motor-actuated type valve in whichthe body is designated generally 30, having an inlet port at 31 and anoutlet port at 32, which are placed in the flow line 20 of the systemabove described so as to convey liquid through the motor valve. A valveseat is located at 33 along a conduit between the inlet and outletports. This valve seat occurs at a restricted portion of the passagefrom which there is a flare as at 34 connecting with the chamber 35.This passage is controlled by a valve plug 36 having a seating surfaceat 37 to engage the seat 33. This plug is taperedon a motor valve to becongreases somewhat sharper taper than the flare 34 and is provided witha plurality of grooves at 38 in order to better resist erosion. Thisvalve plug is power operated and has a stem 39 screw threaded into theplug and extending upwardly therefrom to engage the button 40 on oneside of the diaphragm 41 which is assembled with a button 42 on theotherside of the diaphragm by means of a stud 43 having a flange 44'of a sizeto centralize a spring 45 and which is threaded as at 46 to receive nut47. which through washer 48 binds the two buttons 40 and 42 on thediaphragm 41. An elastic stop nut 49 serves as a check to hold the partsin assembly. 7

The spring 45 which is centralized by the flange 44 engages the innersurface of a recess 56 on the upper portion of the body and serves tourge the valve plug upwardly off of its seat. A plug guide 51 is fittedwithin the body 30 to guide the plug in its reciprocable movement andextends into the bore 55 of the body and has a reduced end to engage ashoulder 56, while a stem guide is prgvided by a flanged nut 57 having ashoulder at 58 to engage a gasket 59 and having threaded engagement withthe body as at 60. A seal 61 of polytetrailu oroethyierie us a y r f t an, i ag s h s em 3. and a boss of this stem guide 51 to serve as a sealagainst the escape of any fluid along the stern, thus leaving anisolated chamber 52 beneath the diaphragm 4 1 The chamber 53 above thisdiaphragm has an entrance port thereto at 54, which port is connected tothe conduit 24 (Fig. 4) extending to the pilot mechanism associated withthe metering check valve.

Th metering shook valve desi nated e e ly 1 in the diagrammatic showing9i Figure .4 has an inlet port 70 (Fig. 2) connected to the condnit 1.5and an outlet P to h boiler 71 connec ed t th c nduit The valve seat.along h c nnect on be ween t e inl t an outlet p rt s ignated 72 an aalve p ug shaped a sh n i gures d 3 is provided to contr thi c nduit byProviding s closure on t seat This villvo pl i de i n g ally 7.3 n compre pposi facing cups 74, 75 with ,a wall 76 between. The lower c p ser esa guide to 11lo e alon t e surface 77 adj n e e t a i P id d w th spacedPa sa s 78, fo r in numb r eauo y d t sh p; t e o the o ph se passages78 serve t perm t a restri ted flow as the valve breaks ofl'its seat andis partially opened.

r j t n o n a dly ooi hi d w ward fa hs s p 7. the e ti of he p u s inthe hape o a cross, a seen in the end view or" this plug in Figure 3.This cross has radially extending fins 7 9 which also serve as guides eng t e sur a e af e he p i en so s to lift the skirt portion 75 clearabove the seat and allow a s bsta ia ly u res ic ,flo h o h th pa es 8.bet en h c o s-s ap ect n a e o e pa t 1 the p The uppe our 4 serves treceive th lo e Port of a pr h 81 h oh 's s a but on 8. h oh i houlde eda 53 n h body o t e g a whi p ng a rd ar... po eeo l 85 fi ed on t e endportion o t e st rn h end S o hioh P esses soon the ha assed i s rt 8 ih reces 8 i the c ntra port n o the r 4 o h plu :3 o as to arse th s aoe do nward y by th e i ien a tio of the pr n 1- Th spr ng se es talways Press th t les downwa dly un es th re is a pressure in the s inshfiioieht to to so t e plug upw rd y ag inst t e notion of th prin a dthus the lug s rves a shoals va ve as e l as me e ing va s wi l :furtherh P h t d nt- The but on \8 ha a ey tendin up ardly h n i whioh i id d ne nal y :by the guide member 91 which, is threaded as at 92 onto thebonnet 93 which is shouldered ,as at '94 to engage a gasket 95 andvvhichiis drawn upwardly by the collar 9.6tl1readed as at 97- to engagethe upper ,end of this bonnet and is drawn upwardly by the screws 98engaging the bottom of5991ptlreghody of the housing. :The stem 86 dlypon a bu on l whi h P e se n oai tubu a Por ion $9 expasses out throughthis bonnet 93 and is sealed as it passes through the guide Q1 by meansof a member 109 of polytetrafluoroethylene, known as Teflon, so that nofluid will pass along the stem 86 and yet the stem will be free to moveupwardly and downwardly in response to the movement of the valve plpgThe stem passes through the space 101 and through the stem guide 162.

This stem 86 also serves as an indicator to denote the position oramount of opening of the valve and thus serves as a metering device. Apointer designated 195 is positioned on the stem 86 between two nuts 106and hio m be ad us d alon he t eads 950.? t stem so as to adjustablyposition the pointer as r d- A a e l may e pl c d at ome convenientlocation for observation so that the position of the valve may be known,and this scale may he graduated as to the volume which is permitted toflow through the valve at difierent positions of the plug 73. Thepressures are maintained within a short range so that thevolumes may hegraduated in this manner. The pressures also rernalh substantiallyconstant so that the valve plug will be opened by the pressure in thesystem in accordance with the amount which may be supplied to the boilerby the regulation of the valve 19. Thus, the spring will permit the plugto open or close in accord'anee with the demand required by the boiler.

In the event thatthe boiler needs a very small arnon nt o water d t u py s r h n a d n erous minimum, this blow-responsive 'metering'valve,inst described, serves to actuate through the pilot valve mechanism 22,which is associated with the metering valve, the motor of control valve21 The mechanism for accomplishing this will now be described.

There is provided a body or casing 110 which is bored to provide thepassages and connecting passages which are required. A pilot valve movesin response to the et ri valve Pro o t am r os odihs. he e o o as to delve liq under Pr s re i om some te n l o e o s e source o h th th boilerl s ater o th upper ohoo h 5. shov he d phra m of h motor (F s a t usehe schoo a ve 21 t a so mo p o o tion w t os oot o the m tors a e.- A.ihd st d i t e d a ra matic view the source of supply is taken frombetween the booster p mp 3 sa th ma n e o Pomp v y a o hdoi 'ZQ'T ohooodhit ente s the asin 1 t 1 an flow a 3.12 the o e .112 h n e th ou tbo e whi h orm d 't .113. the c th o g sh or o min was i l h oo h the boe iorml h on u 15 to the b re 1. 6;

and th n e to the utl por 1 w ch j in he .eondult 4 to h mot r of contrl v lv 21- Alon this atter con uit there s a va ve sea 18 a so a valveph 11 which has a long tapered surface which, as it moves ,upwsrdl w lthither est s h Pehih-a a on t e a iliaseht th s at 1 5, wh le wh n thport o 2 of hep u e es .theses the flow ero ose The ihe s em 12. o P119119 i th ead d at its s oo end 1 a pr ded w t s s s ew .2.8 o h thelever 129 is connected through link 130. This p vot d as a 1. a an a d132 upward i o s the easin 1 a d ex e s lo stem 15.6 whe 'its bi rc ed ed 133 tr ddl s e tem 7 8. a d s in the P of movem o th not 015 so thatwhen the metering valve plug 13 approaches adanse ou n mum flo oo d looth s eve w l bee gaged and s .m vesi o s a t Po n o generation wit t epil t-va v s e 26 s as to l los o th p essure supply to the motor ofvalve 21 which has forced the valve 21 closed, .thus permitting thespring 45 .of valve 2110' open the tvalve in the amount permitted by therelief of pressure in the chamber 53 above it. By this arrangement,should there be any failure of the pilot valve which controls the supplyof pressure to the motor of control valve 21, the failure would permitthe control valve to open and thus fail safe and prevent any harmoccurring by reason of such failure to the main feed pump which thissystem is designed to protect.

As a safety in the system, a second complete shutoff valve is providedby there being formed a valve seat 140 along the conduit 112 and a valveplug 141 is provided with a beveled portion 142 which will engage thisseat and shut 011 the supply of water or pressure to the motor ofcontrol valve 21. This plug also has a taper at 143 to engage a seat at144 and normally is closed on this seat. A stern 145 extends upwardlyfrom the plug 141 and is provided with a cap screw 146 which isconnected to a lever 147 by a link 148. This lever 147 is pivoted at 147and has a set screw 149 in it which is adjustable to engage the foot 150attached to the lever 129 so that should it occur that the regulatingpilot valve should fail at a point just before the metering valvecloses, this shoe 150 would engage and move the lever 147 upwardly todraw the stem 145 upwardly and cause the valve plug 141 to engage seat140 and close off the supply of pressure to the motor of control valve21 so that as an additional safety, should there occur any failure inthe mechanism of the pilot valve which controls the amount supplied tothe motor valve, this mechanism would cause a safe failure.

Lever 129 is pulled downwardly against the stop to keep valve plug 120open by spring 135 and the lever 147 is held downwardly against the stopby spring 151.

The drain systems, above indicated, are for collection of the pure waterand if not contaminated may be run back into the supply which goes tothe tank 11; thus, any drain for this pilot valve mechanism may bere-used if it appears to be non-contaminated. By the arrangementdescribed, I am able to provide an automatic control for boiler feedwater which will prevent burning up of the main feed pump should thesupply to the boiler be reduced to such a minimum that the pump mightotherwise become overheated or explode if its energy were not absorbedsuch as by recirculation. The arrangement is hydraulic as distinguishedfrom electrical and is adaptable for quick shifting of loads and longoperation, it being known that electrical devices fail more frequentlythan the mechanical and hydraulic movements above described.

I claim:

1. In a boiler feed system having a supply reservoir, a boiler, a flowmetering valve movable means coupled thereto, a pump for transferringwater from the reservoir to the boiler through said valve, a by-passconduit from the output of the pump to the reservoir, a normally closedcontrol valve in said conduit having pressure responsive means coupledto said control valve, a second conduit from the output of the pump tosaid pressure responsive means, means in said second conduitcoupled tothe movable means of said metering valve for controlling the pressure insaid second conduit whereby the total water output of said pump may bedivided between the boiler and said bypass conduit in accordance withthe demand of said boiler.

2. A system as in claim 1 wherein said control valve is closed by thepressure responsive means and opened by spring means.

3. A system as in claim 1 wherein said control valve is closed by thepressure responsive means and opened by spring means, and wherein themeans in said second conduit is an auxiliary valve which is closed bythe movable means of the metering valve when the flow through themetering valve falls below a predetermined minimum thereby opening saidcontrol valve.

References Cited in the file of this patent UNITED STATES PATENTS187,825 De Beaurmont Feb. 27, 1877 235,409 Bridges Dec. 14, 1880 688,286Blevney Dec. 10, 1901 1,564,215 Dillig Dec. 8, 1925 2,262,031 Meyer Nov.11, 1941 2,317,091 Adams Apr. 20, 1943 2,397,664 Hillier Apr. 2, 1946

